Mobile communication system, base station, mobile station, and power-saving transmission and reception method used in them

ABSTRACT

There is provided a mobile communication system that can prevent a situation in which, although there is no occasion to receive packets for a mobile station, the reception processing is continued and useless power is undesirably consumed. The mobile communication system includes a base station that repeats a transmission period and a transmission halt period with a constant control cycle, and mobile station that repeats a reception period and a reception halt period with a constant control cycle (antenna, duplexer, reception unit, user data separation unit, packet transmission determination unit, reception period determination unit, packet reception determination unit, and signal synthesis unit). The mobile station alternately repeats the reception period and reception halt period, sends the reception result to the base station, and starts the reception period according to the start of the transmission period of the base station to receive packets. In case all the packets cannot be correctly received during the reception period, the reception period is extended by a predetermined period in the control cycle. Furthermore, in case all the packets can be correctly received during the reception period, the mobile station transfers to the reception halt period to halt the reception.

TECHNICAL FIELD

The present invention relates to a mobile communication system, a basestation, a mobile station, and a power-saving transmission and receptionmethod used in them, and more particularly, to a mobile communicationsystem which changes the ratio of a packet reception period and a packetreception halt period according to the situation of receiving packets soas to save electric power of a mobile station, a base station, a mobilestation, and a power-saving transmission and reception method used inthem.

BACKGROUND ART

In a cellular system, the operable time of a mobile station is dependenton the reception operation and circuit size. From this point of view, asa method to suppress the power consumption of a mobile station,intermittent reception is an effective technique, under which areception circuit is made to operate only when data to be received ispresent, but the reception circuit is made to halt when data to bereceived is not present.

For example, as the first conventional technique, there is employed amethod in which, regarding the intermittent reception of a mobilestation with respect to a traffic under which data is transmitted with asubstantially constant cycle such as the VoIP (Voice over IP) thatcommunicates sound using packets, the standardization is being promotedas the IEEE 802. 16e by the IEEE (Institute of Electrical and ElectronicEngineers) (refer to Non-Patent Document 1).

Under this system, as shown in FIG. 12, the period in which thereception function is halted is referred to as Sleep Window, while thestandby period is referred to as Listening Window, and both of them arerepeated alternately. The Listening Window and Sleep Window arepredetermined fixed time periods. According to this system, the total ofboth the periods being the unit of the repetition of the ListeningWindow and Sleep Window is set to a control cycle, and the intermittentreception of a mobile station is controlled with the control cycle.

According to the intermittent reception system using the Sleep Windowand Listening Window shown in FIG. 12, firstly, a base station or amobile station transmits a message of starting the intermittentreception. Then, the base station transmits a frame number to start theSleep Window to the mobile station, and starts the intermittentreception. After starting the intermittent reception, during the periodof the Listening Window, the base station transmits data to the mobilestation, and the mobile station receives the data. On the other hand,during the period of the Sleep Window, the base station haltstransmitting data to the mobile station, and the mobile station haltsreceiving the data.

Furthermore, as the second conventional technique, under the HSDPA (HighSpeed Downlink Packet Access) system in which the standardization isperformed by the 3GPP (3rd Generation Partnership Project), a receptionmethod of performing the intermittent reception is considered (refer toPatent Document 1).

According to this system, a base station transmits state updateinformation indicative of whether or not reception of packets ispossible for each state update frame, and, when confirming that thestate update information indicates that reception is possible, a mobilestation receives packets. Alternatively, even if the state updateinformation cannot be correctly received due to the fault of thecommunication path, the mobile station receives packets. On the otherhand, when confirming that the state update information indicates thatreception is impossible, the mobile station halts receiving packets.

In both the above-described first and second conventional techniques,there is employed the HARQ (Hybrid Automatic ReQuest) under which, afterreceiving data, the mobile station determines whether or not data isreceived without an error, and transmits the determination result to thebase station as a reception result notification signal. According to theHARQ, the base station can determine whether or not data should beretransmitted based on the reception result notification signaltransmitted from the mobile station, which increases the transmittingefficiency by the retransmission control.

Furthermore, as the third conventional technique, there are disclosed amethod and a system that manage the power consumption within a portableterminal (refer to Patent Document 2). According to the technique, whendata is transmitted, the reception period is extended, while when datais not transmitted, the state is set to the reception halt state.

Furthermore, as the fourth conventional technique, there is disclosed atechnique in which, in a receiving device that performs the intermittentoperation whose reception period is short in the state in which thereception start signal is not received, and extends the reception periodwhen receiving the reception start signal, the power consumption issuppressed to the requisite minimum (refer to Patent Document 3).According to the technique, the cycle of the intermittent operation isextended based on the situation that the reception period is extendeddue to an abnormal signal, and the cycle of the intermittent operationis reduced based on the situation that the reception period is notextended.

[Patent Document 1] JP-A 2004-147050

[Patent Document 2] JP-A 2004-234667

[Patent Document 3] JP-A 10-210563

[Non-Patent Document 1] IEEE P802.16e/D9, June 2005, pp. 164-170

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, in the system in which the fixed reception period and fixedreception halt period are repeated alternately with respect to thetraffic which transmits data with a constant control cycle as theabove-described first conventional technique, there is raised a problemthat, even if all the data is transmitted during the reception period,the reception period cannot be switched to the reception halt period.That is, even if receiving all the packets is completed during thepacket reception period, the mobile station continues the packetreception period until receiving a packet reception halt signal from thebase station. Accordingly, although there is no occasion to receivepackets, power is unnecessarily consumed by continuing the receptionprocessing.

Furthermore, when applying the system of the intermittent reception tothe communication system that performs the retransmission control suchas the HARQ, in case the retransmission is not completed during thereception period, the retransmission is delayed to the reception periodof the next control cycle. Especially, in case of the traffic for whichthe real-time property is required such as the sound communication,there is raised a problem that required conditions are not fulfilled andpackets are broken to lower the QoS (Quality of Service).

Under the above-described second conventional technique, whentransferring to the reception halt state, it is necessary to receive anotification from the base station. Thus, there is raised a problemthat, when the state update information is faulty, since the receptionstate is continued, transition to the reception halt state is delayed.

Similarly, under the above-described third conventional technique, whentransferring to the reception halt state, it is necessary to transmit amessage of the transfer. Further, when the message is faulty, since thereception state is continued, transition to the reception halt state isdelayed. The above-described fourth conventional technique changes thecontrol cycle itself of the intermittent reception, and cannot beapplied to a technique in which it is premised that the control cycle ofthe intermittent reception is constant as the above-described firstconventional technique.

It is therefore an object of the present invention to solve theabove-described problems. Therefore, the present invention has an objectto provide a power-saving transmission and reception system that, in thepacket communication method in which the retransmission control such asthe HARQ is conducted and the reception period and reception halt periodfor packets are repeated alternately with a constant control cycle,elongates the ratio of the reception halt period with respect to thereception period for packets within the control cycle to reduce thepower consumption of a mobile station.

Means for Solving the Problems

To achieve the above-described object, according to the presentinvention, there is provided a mobile communication system includes abase station; and a mobile station, wherein a radio channel is setbetween the base station and mobile station, the base stationalternately repeating a packet transmission period during which packetsare transmitted and a packet transmission halt period during whichtransmission of the packets is halted with a predetermined control cycleat the time of the packet communication using the radio channel, and,after transmitting packets to the mobile station, determining whether ornot retransmission packets should be transmitted based on a receptionresult notification signal from the mobile station, the mobile stationalternately repeating a packet reception period during which packets arereceived and a packet reception halt period during which reception ofthe packets is halted with a predetermined control cycle at the time ofthe packet communication using the radio channel, and sending thereception result with respect to the packets to the base station as thereception result notification signal, wherein the base station includesa packet retransmission means for transmitting the retransmissionpackets with the packet transmission period extended in the controlcycle based on the reception result notification signal, and the mobilestation includes: a packet reception means for receiving the packets bystarting the packet reception period according to the start of thepacket transmission period of the base station; a reception periodextension means for extending the packet reception period in the controlcycle based on the reception result with respect to the packets receivedduring the packet reception period; and a packet reception halt meansfor halting the packet reception by switching from the packet receptionperiod to the packet reception halt period in the control cycle based onthe reception result.

According to the present invention, the reception period extension meansmay include a means for extending the packet reception period by apredetermined time period in the control cycle when receiving thepackets faultily. Furthermore, the reception period extension means mayinclude a means for further extending the packet reception period in thecontrol cycle when the extended packet reception period is shorter thana predetermined reception period. The packet reception halt means maynotify that the packets are correctly received as the reception resultnotification signal, and switch from the packet reception period to thepacket reception halt period in the control cycle when the packetsreceived during the packet reception period are correctly received tohalt the packet reception.

According to the present invention, it is desirable that the packetcommunication using the radio channel is a packet communication by apredetermined service. The base station may further include a means forsending a packet reception halt notification signal to the mobilestation when switching to the packet transmission halt period at thetime of the packet communication by a service other than thepredetermined service, and the mobile station may further include ameans for halting the packet reception by switching from the packetreception period to the packet reception halt period in case ofreceiving the packet reception halt notification signal at the time ofthe packet communication by a service other than the predeterminedservice. The packet communication by the predetermined service may be areal-time communication. The packet communication by a service otherthan the predetermined service may be a non-real-time communication.

According to the present invention, it is desirable that the packetreception period is dynamically changed between a predetermined minimumreception period and a predetermined maximum reception period under thecondition that the control cycle is constant. Furthermore, it isdesirable that the maximum reception period is equal to the controlcycle or lower.

According to the present invention, there is also provided a basestation of a mobile communication system, the base station alternatelyrepeating a packet transmission period during which packets aretransmitted and a packet transmission halt period during whichtransmission of the packets is halted with a predetermined control cycleat the time of the packet communication using a radio channel which isset between the base station and a mobile station, and, aftertransmitting packets to the mobile station, determining whether or notretransmission packets should be transmitted based on a reception resultnotification signal from the mobile station, the base station including:a packet retransmission means for transmitting the retransmissionpackets with the packet transmission period extended in the controlcycle based on the reception result notification signal.

According to the present invention, there is also provided a mobilestation of a mobile communication system, the mobile station alternatelyrepeating a packet reception period during which packets are receivedand a packet reception halt period during which reception of the packetsis halted with a predetermined control cycle at the time of the packetcommunication using a radio channel which is set between the mobilestation and a base station, and sending the reception result withrespect to packets sent from the base station to the base station as areception result notification signal, the mobile station including: apacket reception means for receiving the packets in the packet receptionperiod according to the start of a packet transmission period of thebase station; a reception period extension means for extending thepacket reception period in the control cycle based on the receptionresult with respect to the packets received during the packet receptionperiod; and a packet reception halt means for halting the packetreception by switching from the packet reception period to the packetreception halt period in the control cycle based on the receptionresult.

According to the present invention, there is also provided apower-saving transmission and reception method for a mobilecommunication system, comprising: setting a radio channel between a basestation and a mobile station, at the base station, alternately repeatinga packet transmission period during which packets are transmitted and apacket transmission halt period during which transmission of the packetsis halted with a predetermined control cycle at the time of the packetcommunication using the radio channel, and, after transmitting packetsto the mobile station, determining whether or not retransmission packetsshould be transmitted based on a reception result notification signal;at the mobile station, alternately repeating a packet reception periodduring which the packets are received and a packet reception halt periodduring which reception of the packets is halted with a predeterminedcontrol cycle at the time of the packet communication using the radiochannel, and sending the reception result with respect to the packets tothe base station as the reception result notification signal; at thebase station, transmitting the retransmission packets with the packettransmission period extended in the control cycle based on the receptionresult notification signal; at the mobile station, receiving the packetsin the packet reception period according to the start of the packettransmission period of the base station; extending the packet receptionperiod in the control cycle based on the reception result with respectto the packets received during the packet reception period; and haltingthe packet reception by switching from the packet reception period tothe packet reception halt period in the control cycle based on thereception result.

According to the present invention, there is also provided apower-saving transmission and reception method for a base station,comprising: alternately repeating a packet transmission period duringwhich packets are transmitted and a packet transmission halt periodduring which transmission of the packets is halted with a predeterminedcontrol cycle at the time of the packet communication using a radiochannel which is set between the base station and a mobile station, and,after transmitting packets to the mobile station, determining whether ornot retransmission packets should be transmitted based on a receptionresult notification signal from the mobile station; and transmitting theretransmission packets with the packet transmission period extended inthe control cycle based on the reception result notification signal.

According to the present invention, there is also provided apower-saving transmission and reception method for a mobile station,comprising: alternately repeating a packet reception period during whichpackets are received and a packet reception halt period during whichreception of the packets is halted with a predetermined control cycle atthe time of the packet communication using a radio channel which is setbetween the mobile station and a base station, and sending the receptionresult with respect to the packets sent from the base station to thebase station as a reception result notification signal: receiving thepackets in the packet reception period according to the start of apacket transmission period of the base station; extending the packetreception period in the control cycle based on the reception result withrespect to the packets received during the packet reception period; andhalting the packet reception by switching from the packet receptionperiod to the packet reception halt period in the control cycle based onthe reception result.

According to the present invention, there is also provided apower-saving transmission and reception program for a base station, thebase station alternately repeating a packet transmission period duringwhich packets are transmitted and a packet transmission halt periodduring which transmission of the packets is halted with a predeterminedcontrol cycle at the time of the packet communication using a radiochannel which is set between the base station and a mobile station, and,after transmitting packets to the mobile station, determining whether ornot retransmission packets should be transmitted based on a receptionresult notification signal from the mobile station, the program enablinga computer to execute: a step of transmitting the retransmission packetswith the packet transmission period extended in the control cycle basedon the reception result notification signal.

According to the present invention, there is also provided apower-saving transmission and reception program for a mobile station,the mobile station alternately repeating a packet reception periodduring which packets are received and a packet reception halt periodduring which reception of the packets is halted with a predeterminedcontrol cycle at the time of the packet communication using a radiochannel which is set between the mobile station and a base station, andsending the reception result with respect to the packets sent from thebase station to the base station as a reception result notificationsignal, the program enabling a computer to execute: a step of receivingthe packets in the packet reception period according to the start of apacket transmission period of the base station; a step of extending thepacket reception period in the control cycle based on the receptionresult with respect to the packets received during the packet receptionperiod; and a step of halting the packet reception by switching from thepacket reception period to the packet reception halt period in thecontrol cycle based on the reception result.

Advantages of the Invention

According to the present invention, in the packet communication methodin which the reception period and the reception halt period for packetsare alternately repeated with a constant control cycle, it is possibleto provide a power-saving transmission and reception system that canelongate the reception halt period with respect to the reception periodfor packets in the control cycle to reduce the power consumption of amobile station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a view indicative of a mobile communication systemaccording to the first exemplary embodiment of the present invention;

FIG. 2 shows a block diagram indicative of the configuration of a basestation according to the first exemplary embodiment of the presentinvention;

FIG. 3 shows a block diagram indicative of the configuration of a mobilestation according to the first exemplary embodiment of the presentinvention;

FIG. 4 shows a flowchart indicative of the operation of the base stationshown in FIG. 2;

FIG. 5 shows a flowchart indicative of the operation of the mobilestation shown in FIG. 3;

FIGS. 6A and 6B show a schematic diagram to explain a control cycle forthe intermittent reception of the mobile station with a predeterminedstart timing;

FIG. 7A to FIG. 7D show schematic views indicative of the state of theextension of the packet reception period;

FIG. 8 shows a block diagram indicative of the configuration of a basestation according to the second exemplary embodiment of the presentinvention;

FIG. 9 shows a block diagram indicative of the configuration of a mobilestation according to the second exemplary embodiment of the presentinvention;

FIG. 10 shows a flowchart indicative of the operation of the basestation shown in FIG. 8;

FIG. 11 shows a flowchart indicative of the operation of the mobilestation shown in FIG. 9; and

FIG. 12 shows a schematic diagram to explain the intermittent receptionsystem using the Listening Window and Sleep Window of a conventionalexample.

EXPLANATION OF REFERENCE SYMBOLS

-   1: Base station-   2: Mobile station-   3: Radio channel-   11, 21: Antenna-   12, 22: Duplexer-   13, 23: Reception unit-   14, 24: User data separation unit-   15: Packet transmission control unit-   16: Signal generation unit-   17, 29: Transmission unit-   18, 30: Call control unit-   25: Packet reception determination unit-   26: Reception period determination unit-   27: Packet control signal generation unit-   28: Signal synthesis unit

BEST MODE FOR CARRYING OUT THE INVENTION

Now, preferred exemplary embodiments of the present invention will bedescribed by referring to the accompanying drawings.

First Exemplary Embodiment

FIG. 1 shows a view indicative of the configuration of a mobilecommunication system according to the first exemplary embodiment of thepresent invention.

In FIG. 1, the mobile communication system according to the presentexemplary embodiment is used in a cellular system, and includes a basestation 1 and a mobile station 2. Between the base station 1 and themobile station 2, a radio channel 3 to transmit and receive user dataand control data by employing the packet communication can be set. Forthe access system of the packet communication by the radio channel 3,any type may be applied, and, for example, the CDMA (Code DivisionMultiple Access) system etc. is employed. The mobile station 2 isconfigured by a cellular phone, a portable terminal such as a PHS(Personal Handyphone System) or a PDA (Personal Digital Assistant), or amobile terminal such as an in-vehicle monitor.

FIG. 2 shows a block diagram indicative of the internal configuration ofthe base station 1 shown in FIG. 1.

In FIG. 2, the base station 1 includes an antenna 11, a duplexer (DUP)12 connected to the antenna 11, a reception unit 13 and a transmissionunit 17 connected to the DUP 12, and a user data separation unit 14connected to the output side of the reception unit 13. Furthermore, thebase station 1 includes a packet transmission control unit 15 connectedto the output side of the user data separation unit 14, and a signalgeneration unit 16 connected to the output side of the packettransmission control unit 15 and to the input side of the transmissionunit 17. As for other configurations, since heretofore known techniquescan be applied, the explanation is omitted.

The reception unit 13 receives a signal transmitted from the mobilestation 2 using the radio channel 3 through the antenna 11 and duplexer12, and outputs thus received signal to the user data separation unit14.

The user data separation unit 14 separates the signal input from thereception unit 13 into user data and a control signal, and outputs theuser data to a user data output unit (not shown), and the controlinformation to the packet transmission control unit 15.

The packet transmission control unit 15 sends the reception state ofpackets which have been transmitted already using the controlinformation separated by the user data separation unit 14 to the signalgeneration unit 16. Furthermore, in the intermittent reception state ofthe mobile station 2 using a control cycle to be described later, thepacket transmission control unit 15 determines whether or not the stateis in a period in which data to be transmitted (new data orretransmission data) can be transmitted (or retransmitted) by employinga method to be described later as an example, and also sends informationas to whether or not data can be transmitted being the determinationresult to the signal generation unit 16.

The signal generation unit 16 determines the transmission possibilityand the presence of retransmission of packets based on the informationreceived from the packet transmission control unit 15, and, in casetransmission of packets is possible based on the result, outputs userdata input from a user data input unit (not shown) to the transmissionunit 17. Then, the transmission unit 17 transmits packets being the userdata from the antenna 11 through the duplexer 12.

FIG. 3 shows a block diagram indicative of the internal configuration ofthe mobile station 2 shown in FIG. 1.

In FIG. 3, the mobile station 2 includes an antenna 21, a duplexer (DUP)22 connected to the antenna 21, a reception unit 23 and a transmissionunit 29 connected to the DUP 22, and a user data separation unit 24connected to the output side of the reception unit 23. In addition, themobile station 2 includes a packet reception determination unit 25connected to the output side of the user data separation unit 24, areception period determination unit 26 connected to the output side ofthe packet reception determination unit 25 and to the input side of thereception unit 23, and a packet control signal generation unit 27connected to the output side of the packet reception determination unit25. Furthermore, the mobile station 2 includes a signal synthesis unit28 connected to the output side of the reception period determinationunit 26 and packet control signal generation unit 27 and to the inputside of the transmission unit 29. As for other configurations, sinceheretofore known techniques can be applied, the explanation is omitted.

The reception unit 23 receives a signal transmitted from the basestation 1 using the radio channel 3 through the antenna 21 and duplexer22, and outputs thus received signal to the user data separation unit24.

The user data separation unit 24 separates the signal input from thereception unit 23 into user data and a control signal, and outputs theuser data to a user data output unit (not shown), and outputs thecontrol information to the packet reception determination unit 25,respectively.

The packet reception determination unit 25 determines whether or notuser data received from the base station 1 is correctly received basedon the control information separated by the user data separation unit 24by employing an error detection function to be described later as anexample, and sends the determination result to the reception perioddetermination unit 26 and packet control signal generation unit 27.

The reception period determination unit 26 determines whether or not thepacket reception period should be extended based on the inputdetermination result by employing a method to be described later as anexample, and sends the determination result to the reception unit 23 andsignal synthesis unit 28.

The packet control signal generation unit 27 generates a receptionconfirmation signal (reception result notification signal) for packetsbased on the determination result input from the reception perioddetermination unit 26, and sends the packet reception confirmationsignal to the signal synthesis unit 28.

The signal synthesis unit 28 synthesizes the packet receptionconfirmation signal from the packet control signal generation unit 27and user data input from a user data input unit (not shown), and outputsthus synthesized signal to the transmission unit 29 based on thedetermination result by the reception period determination unit 26.Then, the transmission unit 29 transmits packets obtained bysynthesizing the packet reception confirmation signal and user data fromthe antenna 21 through the duplexer 22. In this case, the packetreception confirmation signal and user data are synthesized to betransmitted. On the other hand, they may be separately transmittedwithout synthesizing them.

At least part of functions of the respective units of the base station 1and mobile station 2 may be realized by a computer using a program. Thisprogram may be read out from a recording medium to be loaded to acomputer, or may be transmitted through a communication network to beloaded to a computer.

FIG. 4 shows a flowchart indicative of the operation of the base station1, and FIG. 5 shows a flowchart indicative of the operation of themobile station 2. The present exemplary embodiment is equal to theabove-described first conventional technique in that a control cycle isset for the transmission period and transmission halt period, or for thereception period and reception halt period. Accordingly, it is assumedthat the start timing of the control cycle of the base station 1 andthat of the mobile station 2 are known mutually, and the operation willbe explained.

Firstly, referring to FIG. 4, the operation of the base station 1 willbe explained. This operation is realized when a computer in the basestation 1, as a means to accomplish at least part of functions of therespective units of the base station 1 as an example, executes a commandof a preset control program (which corresponds to a power-savingtransmission and reception program of the base station according to thepresent invention). In this example, the control program is previouslystored in a recording medium such as a ROM (Read Only Memory), and acommand thereof is read out to be executed by a computer at the time ofthe operation.

When starting a power saving mode (intermittent reception state), asshown in FIG. 6A, the base station 1 starts a control cycle Ta for theintermittent reception of the mobile station 2 with a predeterminedstart timing ta, and starts the transmission with the control cycle Ta.In this case, the base station 1 repeats a packet transmission periodTa1 to transmit packets to the mobile station 2 and a packettransmission halt period Ta2 to halt transmitting packets with theconstant control cycle Ta alternately, and controls the packettransmission operation. The control cycle Ta is the total (Ta1+Ta2) ofboth the periods Ta1, Ta2 being the unit of the repetition of the packettransmission period Ta1 and packet transmission halt period Ta2. Thecontrol cycle Ta remains constant and is not changed during theoperation. On the other hand, the ratio of the packet transmissionperiod Ta1 and the packet transmission halt period Ta2 in the controlcycle Ta can be dynamically changed during the operation, as will bedescribed hereinafter. Controlling the packet transmission with thecontrol cycle Ta is mainly performed by the respective operations of thepacket transmission control unit 15 and signal generation unit 16.

In FIG. 4, after starting the control cycle Ta with the predeterminedstart timing ta (step S101), the base station 1 determines whether ornot the period is within a minimum reception period Tbmin (refer tosubsequent description) corresponding to the minimum value of apredetermined packet reception period Tb1 (refer to subsequentdescription) of the mobile station 2 (step S102). This determination ismainly performed by the operation of the packet transmission controlunit 15. As the minimum reception period Tbmin, the minimum value of thepacket reception period Tb1 which has been previously determined betweenthe base station 1 and the mobile station 2 is used. This minimum valueis stored, for example, in a memory (not shown) of the packettransmission control unit 15.

By the determination in step S102, when the determination is YES (withinminimum reception period Tbmin), it is determined whether or not packets(retransmission packets or new packets) to be transmitted are detected(step S103). This determination is performed by the signal generationunit 16. As a result, in case packets to be transmitted are detected(step S103: YES), the signal generation unit 16 transmits thecorresponding packets through the transmission unit 17, DUP 12, andantenna 11 (step S104), and the processing returns to step S102 torepeat the similar operation. On the other hand, in case packets to betransmitted are not detected (step S103: NO), the processing returns tostep S102 to repeat the similar operation.

Next, when the minimum reception period Tbmin elapses, and thedetermination is NO (not within minimum reception period Tbmin) in stepS102, the base station 1 confirms whether or not retransmission packetsare present afterward (step S105). The presence or absence ofretransmission packets is determined based on a packet receptionconfirmation signal transmitted from the mobile station 2. Thedetermination in step S105 is mainly performed by the operation of thesignal generation unit 16.

Accordingly, when retransmission packets are present (step S105: YES),it is determined whether or not the packet reception period Tb1 (referto subsequent description) of the mobile station 2 can be extended (stepS106). The determination of the extension possibility of the packetreception period Tb1 is performed by comparing the period with apredetermined maximum reception period Tbmax (refer to subsequentdescription) of the mobile station 2. In this case, in case of beingwithin the maximum reception period Tbmax, it is determined thatextension of the packet reception period Tb1 is possible, and, in caseof being over the maximum reception period Tbmax, it is determined thatextension of the packet reception period Tb1 is impossible. As themaximum reception period Tbmax, the maximum value of the packetreception period Tb1 which has been previously determined between thebase station 1 and the mobile station 2 is used. This maximum value isstored, for example, in a memory (not shown) of the packet transmissioncontrol unit 15. The determination in step S106 is mainly performed bythe operation of the packet transmission control unit 15.

By the determination in step S106, in case extending the packetreception period Tb1 of the mobile station 2 is possible (step S106;YES), the processing goes to step S104, and the signal generation unit16 transmits corresponding retransmission packets through thetransmission unit 17, DUP 12, and antenna 11. In this time period, thepacket transmission period Ta1 in the control cycle Ta is extended andupdated. Extension of the packet transmission period Ta1 is possibleuntil getting to the maximum reception period Tbmax.

On the other hand, by the determination in step S105, in caseretransmission packets are absent (step S105: NO), or, by thedetermination in step S105, in case the packet reception period Tb1 ofthe mobile station 2 cannot be extended (step S106: NO), the packettransmission period Ta1 in the control cycle Ta is transferred to thepacket transmission halt period Ta2, and transmission of packets ishalted. The halt of packet transmission is continued until the packettransmission halt period Ta2 ends, that is, until the control cycle Taof this time ends (step S107). The processing during this time period ismainly performed by the operations of the packet transmission controlunit 15 and signal generation unit 16.

After the control cycle Ta ends in step S107, it is determined whetheror not the power saving mode should be ended (step S108). Thisdetermination is performed by the operation of the packet transmissioncontrol unit 15. As a result, in case of not ending the power savingmode (step S108: NO), the processing returns to step S101 to start thenext control cycle Ta, and repeats the similar operation. On the otherhand, in case of ending the power saving mode (step S108: YES),transmission with the control cycle Ta is ended.

Next, referring to FIG. 5, the operation of the mobile station 2 will beexplained. This operation is realized when a computer in the mobilestation 2, as a means to accomplish at least part of functions of therespective units of the mobile station 2 as an example, executes acommand of a preset control program (which corresponds to a power-savingtransmission and reception program of the mobile station according tothe present invention). In this example, a control program is previouslystored in a recording medium such as a ROM, and a command thereof isread out to be executed by a computer at the time of the operation.

Similar to the operation of the base station 1, when starting the powersaving mode, the mobile station 2 starts a control cycle Tb for theintermittent reception with a predetermined start timing tbcorresponding to the start timing ta of the packet transmission periodTa1 of the base station 1, and starts the reception with the controlcycle Tb. In this case, as shown in FIG. 6B, the mobile station 2repeats a packet reception period Tb1 to receive packets and a packetreception halt period Tb2 to halt receiving packets with the constantcontrol cycle Tb alternately, and controls the packet receptionoperation. The control cycle Tb for the intermittent reception is thetotal (Tb1+Tb2) of both the periods Tb1, Tb2 being the unit of therepetition of the packet reception period Tb1 and packet reception haltperiod Tb2. The control cycle Tb remains constant and is not changedduring the operation. On the other hand, the ratio of the packetreception period Tb1 and the packet reception halt period Tb2 in thecontrol cycle Tb can be dynamically changed during the operation, aswill be described hereinafter. Controlling the packet reception with thecontrol cycle Tb is mainly performed by the respective operations of thepacket reception determination unit 25, reception period determinationunit 26, packet control signal generation unit 27, signal synthesis unit28, and reception unit 23.

In FIG. 5, when starting the control cycle Tb with the predeterminedstart timing tb (step S201), the mobile station 2 sets the packetreception period Tb1 in the control cycle Tb to the minimum receptionperiod Tbmin which is the predetermined minimum value (step S202). Theset value of the minimum reception period Tbmin is stored, for example,in a memory (not shown) of the reception period determination unit 26.

Next, the mobile station 2 receives packets transmitted from the basestation 1 through the antenna 21, DUP 22, and reception unit 23 duringthe minimum reception period Tbmin being the set packet reception periodTb1, and, at the time the minimum reception period Tbmin ends, confirmswhether or not all the received packets are correctly received (stepS203). This confirmation is mainly performed by the respectiveoperations of the packet reception determination unit 25 and receptionperiod determination unit 26. In this confirmation, the confirmationwhether or not all the received packets are correctly received isperformed by, using a known error detection function as an example,detecting whether or not an error is present in the received packets. Inthis case, when it is detected that an error is not present in thereceived packets, it is determined that the packets are correctlyreceived, while when it is detected that an error is present in thereceived packets, it is determined that the packets are not correctlyreceived, that is, the packets are faultily received.

As a result, in case all the packets are correctly received (step S203:YES), the packet reception period Tb1 in the control cycle Tb istransferred to the packet reception halt period Tb2, and receivingpackets is halted. The halt of packet reception is continued until thepacket reception halt period Tb2 ends, that is, until the control cycleTb of this time ends (step S204). The processing during this time periodis mainly performed by the respective operations of the reception perioddetermination unit 26 and reception unit 23.

On the other hand, in case there are some packets which are notcorrectly received (step S203: NO), it is determined whether or not thepacket reception period Tb1 can be extended (step S205). Thedetermination of the extension possibility of the packet receptionperiod Tb1 is performed by comparing the period with a predeterminedmaximum reception period Tbmax. In this case, the maximum receptionperiod Tbmax may be a value so long as the value is not over the controlcycle Tb. The determination in step S205 is mainly performed by theoperation of the reception period determination unit 26.

By the determination in step S205, in case extending the packetreception period Tb1 is possible (step S205: YES), the packet receptionperiod Tb1 is extended and updated (step S206). The packet receptionperiod Tb1 is updated by updating the set value of the minimum receptionperiod Tbmin stored, for example, in a memory (not shown) of thereception period determination unit 26.

Next, it is confirmed whether or not all the retransmission packetstransmitted from the base station 1 through the antenna 21, DUP 22, andreception unit 23 are correctly received during the updated packetreception period Tb1 (step S207). This confirmation is mainly performedby the operation of the reception period determination unit 26.

As a result, in case all the retransmission packets are correctlyreceived during the updated packet reception period Tb1 (step S207:YES), the packet reception period Tb1 in the control cycle Tb istransferred to the packet reception halt period Tb2, and halts receivingpackets. The halt of packet reception is continued until the packetreception halt period Tb2 ends, that is, the control cycle Tb of thistime elapses (step S204). The processing during this time period ismainly performed by the respective operations of the reception perioddetermination unit 26 and reception unit 23.

On the other hand, in case all the retransmission packets are notcorrectly received during the updated packet reception period Tb1 (stepS207: NO), the processing returns to step S205 to repeat the similaroperation, and the updated packet reception period Tb1 is furtherextended and updated.

FIG. 7A to FIG. 7D show schematic views indicative of the state of theextension of the packet reception period Tb1.

In the example shown in FIG. 7A, the packet reception period Tb1 startsat a start timing to of the control cycle Tb, and ends at an end timepoint t1 of the minimum reception period Tbmin. On the other hand, inthe example shown in FIG. 7B, the packet reception period Tb1 starts atthe start timing to of the control cycle Tb, and ends at an extendedtime point t2 which is a time point extended from the end time point t1of the minimum reception period Tbmin. Furthermore, in the example shownin FIG. 7C, the packet reception period Tb1 starts at the start timingto of the control cycle Tb, and ends at an extended time point t3 whichis a time point further extended from the extended time point t2.Moreover, in the example shown in FIG. 7D, the packet reception periodTb1 starts at the start timing to of the control cycle Tb, and ends atan end time point t4 of the maximum reception period Tbmax.

In this way, the extension of the packet reception period Tb1 is updateddynamically between the minimum reception period Tbmin and the maximumreception period Tbmax in the control cycle Tb. In the example shown inFIG. 7D, for the sake of convenience in explanation, the maximumreception period Tbmax is set shorter than the control cycle Tb. On theother hand, the maximum reception period Tbmax may be set equal to thecontrol cycle Tb at a maximum.

After the control cycle Tb ends in step S204, it is determined whetheror not the power saving mode should be ended (step S208). As a result,in case of not ending the power saving mode (step S208: NO), theprocessing returns to step S101 to start the reception by the nextcontrol cycle Tb, and repeats the similar operation. On the other hand,in case of ending the power saving mode, reception with the controlcycle Tb is ended.

In this way, according to the present exemplary embodiment, in startingthe control cycle Tb of the intermittent reception, in case all thepackets received during the minimum reception period Tbmin are correctlyreceived, the mobile station 2 can transfer the packet reception periodTb1 to the packet reception halt period Tb2 automatically when theminimum reception period Tbmin ends, and halt receiving packets. In thisway, the mobile station 2 can automatically transfer to the receptionhalt state without receiving an explicit designation signal (receptionhalt notification signal) from the base station. Similarly, during theextended period of the packet reception period Tb1 in the control cycleTb after the minimum reception period Tbmin elapses, since it isdetermined whether or not all the packets are successfully received, themobile station 2 can automatically transfer to the reception halt statewithout receiving an explicit designation signal from the base station.

Accordingly, the mobile station 2 does not have to receive the receptionhalt notification signal from the base station 1, and a time periodbefore receiving the reception halt notification signal can be halted.In this way, a situation in which, although there is no occasion toreceive packets, the reception processing is continued and useless poweris undesirably consumed can be considerably prevented.

Furthermore, in the above-described conventional technique, in case ofreceiving the reception halt notification signal, when the notificationsignal is faulty, the packet reception period Tb1 continues. On theother hand, according to the present exemplary embodiment, since thereception halt notification signal is unnecessary, the problem that thepacket reception period Tb1 continues due to the faulty notificationsignal can be solved. As a result, in the constant control cycle Tb, thepacket reception halt period Tb2 can be made long relatively withrespect to the packet reception period Tb1, which can reduce the powerconsumption.

Second Exemplary Embodiment

FIG. 8 shows a block diagram indicative of the configuration of a basestation of a mobile communication system according to the secondexemplary embodiment of the present invention. FIG. 9 shows a blockdiagram indicative of the configuration of a mobile station of themobile communication system.

In FIG. 8, a call control unit 18 is added to the configuration of theabove-described base station shown in FIG. 2. Similarly, in FIG. 9, acall control unit 30 is added to the configuration of theabove-described mobile station shown in FIG. 3. Other configurations aresimilar to those in the first exemplary embodiment, and the samereference numerals are appended thereto and detailed explanation ofwhich will be omitted.

In the base station 1 shown in FIG. 8, the call control unit 18determines whether or not a reception halt signal should be transmittedto the mobile station 2 depending on a service to be communicated. Forexample, the base station 1 determines a communication service (stepS301), as shown in FIG. 10, and, in case the communication servicecorresponds to a service that performs real-time communication such asthe VoIP, in order to perform the operation of the intermittentreception of the mobile station 2, the base station 1 does not transmitthe reception halt signal (step S302). On the other hand, in case thecommunication service corresponds to a service that performsnon-real-time communication such as the FTP (File Transfer Protocol) orWeb browsing, the operation of the intermittent reception of the mobilestation 2 is not performed, and the base station 1 transmits thereception halt signal after it is confirmed that the mobile station 2can receive a signal using the reception confirmation signal from themobile station 2 (step S303).

On the other hand, in the mobile station 2 shown in FIG. 9, the callcontrol unit 30 switches the operation of the reception unit 23depending on a communication service. For example, the call control unit30 determines a communication service (step S401), as shown in FIG. 11,and, in case the communication service corresponds to a service thatperforms real-time communication such as the VoIP, executes theoperation of the intermittent reception similar to the above-describedfirst exemplary embodiment without receiving the notification of thereception halt signal (step S402). On the other hand, in case thecommunication service corresponds to a service that performsnon-real-time communication such as the FTP or Web browsing, the mobilestation 2 does not perform the operation of the intermittent reception,and is made to transfer to the reception halt state after receiving thereception halt signal from the base station 1 (step S403).

While the respective operations of the base station 1 and mobile station2 are switched depending on a communication service, since the settingof a communication service and the operation in case of thenon-real-time communication can be realized using heretofore knowntechniques, and explanation of which will be omitted.

In this case, in the non-real-time communication, the transmission cyclefor data is not constant. Accordingly, when the mobile stationautomatically transfers to the reception halt state, there is raised apossibility that the delay becomes large since the reception is haltedat a timing when the reception is not originally halted. As a result,influence on the characteristics such as the throughput becomes large.Thus, in the non-real-time communication, it is required to send thereception halt notification from the base station to the mobile station.On the other hand, in the real-time communication, data is transmittedwith a substantially constant cycle. Thus, when data can be receivedwithin a constant period, there is no influence on the characteristicseven if the reception is halted afterward, and it is not necessarilyrequired to send the reception halt notification from the base stationto the mobile station.

In this way, according to the present exemplary embodiment, since theautomatic halt is not performed in the non-real-time communication, theproblem of the lowering of the throughput can be prevented. Furthermore,by employing the present invention to the real-time communication, ascompared with the case of employing the present invention to thenon-real-time communication, the effect of elongating the reception haltperiod becomes significantly large by automatically halting reception.

In the above-described exemplary embodiment, while the call setting unitis arranged in both the base station and mobile station, a similaroperation is possible when the call setting unit is arranged in any oneof the base station and mobile station.

Furthermore, in the above-described exemplary embodiment, the operationof the intermittent reception is not performed when a communicationservice is the non-real-time communication, and the operation of theintermittent reception is performed when a communication service is thereal-time communication. The control is changed in the non-real-timecommunication and real-time communication. The present invention is notrestricted to this, and may be applied to a case in which the control ischanged according to the sort of communication services, that is, theoperation of the intermittent reception is performed for specificcommunication services and the operation of the intermittent receptionis not performed for other communication services.

For example, it is possible to change the control for the case in whichthe communication of a communication service is high in priority and forthe case in which the communication of a communication service is low inpriority. In this case, the control may be performed so that, in casethe communication of a communication service is high in priority, theoperation of the intermittent reception is not performed similar to thecase of the non-real-time communication, while in case the communicationof a communication service is low in priority, the operation of theintermittent reception is performed similar to the case of the real-timecommunication.

As described above, while the respective exemplary embodiments accordingto the present invention have been described, the present invention isnot limited to the above-described representative exemplary embodiments.It should be understood by those ordinary skilled in the art thatvarious modifications and alternative constructions can be implementedwithout departing from the scope and spirit of the present inventionbased on the appended claims, and these modifications and alternativeconstructions belong to the range of right of the present invention.

INDUSTRIAL APPLICABILITY

The present invention can be applied to a mobile communication system, abase station, a mobile station, and a power-saving transmission andreception method and a power-saving transmission and reception programused in them. Especially, the present invention can be applied to amobile communication system which changes the ratio of the packetreception period and the packet reception halt period according to thesituation of receiving packets so as to save electric power of a mobilestation, a base station, a mobile station, and a power-savingtransmission and reception method and a power-saving transmission andreception program used in them.

The invention claimed is:
 1. A mobile station which communicates with abase station using a radio channel, the mobile station comprising: aswitching unit configured to switch from a packet reception period,during which packet reception can be executed, to a packet receptionhalt period, during which packet reception is halted; a transmissionunit configured to transmit, to the base station, a result of receivinga packet sent from the base station, as a reception result notificationsignal; a packet reception determination unit configured to determine apacket reception fault; and a reception period determination unitconfigured to extend the packet reception period if the packet receptionfault is determined by the packet reception determination unit; wherein,if the packet reception period is extended, the packet reception haltperiod following the packet reception period is shortened.
 2. The mobilestation according to claim 1, wherein the packet reception period andthe packet reception halt period are alternately repeated.
 3. The mobilestation according to claim 2, wherein the packet reception period andthe packet reception halt period comprise a periodic control cyclehaving a fixed period.
 4. The mobile station according to claim 1,wherein the packet reception period is further extended if anotherpacket reception fault is determined during a retransmission.
 5. Amobile communication system comprising: a base station; and a mobilestation wherein the base station comprises: a setting unit configured toset a radio channel between the base station and the mobile station; anda communication unit configured to communicate with the mobile stationusing the radio channel; wherein the mobile station comprises: aswitching unit configured to switch from a packet reception period,during which packet reception can be executed, to a packet receptionhalt period, during which packet reception is halted; a transmittingunit configured to transmit, to the base station, a result of receivinga packet sent from the base station, as a reception result notificationsignal; a packet reception determination unit configured to determine apacket reception fault; and a reception period determination unitconfigured to extend the packet reception period if the packet receptionfault is determined by the packet reception determination unit; wherein,if the packet reception period is extended, the packet reception haltperiod following the packet reception period is shortened.
 6. The mobilecommunication system according to claim 5, wherein the packet receptionperiod and the packet reception halt period are alternately repeated. 7.The mobile communication system according to claim 6, wherein the packetreception period and the packet reception halt period comprise aperiodic control cycle having a fixed period.
 8. The mobilecommunication system according to claim 5, wherein the packet receptionperiod is further extended if another packet reception fault isdetermined during a retransmission.
 9. A method for controlling a mobilestation which communicates with a base station using a radio channel,the method comprising: switching from a packet reception period duringwhich packet reception can be executed, to a packet reception haltperiod, during which packet reception is halted; transmitting, to thebase station, a result of receiving a packet sent from the base station,as a reception result notification signal; determining a packetreception fault; and extending the packet reception period if the packetreception fault is determined; wherein, if the packet reception periodis extended, the packet reception halt period following the packetreception period is shortened.
 10. The method according to claim 9,wherein the packet reception period and the packet reception halt periodare alternately repeated.
 11. A method for controlling a mobilecommunication system which includes at least a base station and a mobilestation, the method comprising: the base station setting a radio channelbetween the base station and the mobile station; the base stationcommunicating with the mobile station using the radio channel; themobile station switching from a packet reception period, during whichpacket reception can be executed, to a packet reception halt period,during which packet reception is halted; the mobile stationtransmitting, to the base station, a result of receiving a packet sentfrom the base station, as a reception result notification signal; themobile station determining a packet reception fault; and the mobilestation extending the packet reception period if the packet receptionfault is determined by the mobile station; wherein, if the packetreception period is extended, the packet reception halt period followingthe packet reception period is shortened.
 12. The method according toclaim 11, wherein the packet reception period and the packet receptionhalt period are alternately repeated.
 13. A non-transitorycomputer-readable information recording medium storing a program which,when executed by a processor, performs a method for controlling a mobilestation which communicates with a base station using a radio channel,the method comprising: switching from a packet reception period, duringwhich packet reception is can be executed, to a packet reception haltperiod, during which packet reception is halted; transmitting, to thebase station, a result of receiving a packet sent from the base station,as a reception result notification signal; determining a packetreception fault; and extending the packet reception period if the packetreception fault is determined; wherein, if the packet reception periodis extended, the packet reception halt period following the packetreception period is shortened.
 14. The non-transitory computer-readableinformation recording medium according to claim 13, wherein the packetreception period and the packet reception halt period are alternatelyrepeated.